how to convert a symbolic function into type double

hi there, i have a symbolic function in the form y= A *(B*t + exp(t)) + ph(t), where ph is also symbolic, and i want to compare it with experimental data in order to estimate the values of the parameters A and B. When i call the lsqcurvefit command i am told that the input y should be of data type double. how can i deal with this ??

[Star Strider]

You have to define ‘ph’ as a function of t, and incorporate it into your ‘y’ function. The lsqcurvefit function requires that ‘y’ be a function file or an anonymous function, and in a specific format, not a symbolic function.

[maria]

ph(t) is defined previsouvly in the code but even when i write y= A *(B*t + exp(t)), the problem still remains. lsqcurvefit doesn't accept symbolic functions, so how am i supposed to convert it into type double and estimate the parameters ??